Individual dosimeters

CHEMICAL DOSIMETERS

These patches can be applied directly onto the skin of volunteers. The key component in most patches is polysulfone which is degraded by UV radiation (especially UVB).

Advantages:

  • Good estimation of the actual exposure of individuals,
  • Can be applied on specific anatomical body site.

Disadvantages:

  • High set-up cost (the patches are inexpensive, but the logistics required for the measurement is important and costly),
  • Patches can easily saturate, requiring replacement once- or twice-daily on days of strong sunshine.
  • UVA and UVB are not clearly distinguished.

BIOLOGICAL DOSIMETERS

A biological dosimeter performs an integrated measure of UV radiation during a given exposure time by using mutation induction in microorganisms (bacillus subtilis, bacteriophages).

Advantages:

  • Good estimation of the actual exposure of individuals,
  • Can be applied on specific anatomical body site.

Disadvantages:

  • Long lead times required for the analysis of received dose,
  • High management costs,
  • Must be replaced during the day.

Images of biological dosimeters are available here: www.biosense.de

ELECTRONIC DOSIMETERS

Electronic dosimeters are fitted with sensors able to separate UVA and UVB rays, either in the form of a wrist watch or in a cased box to be placed next to the individual during exposure.

Electronic dosimeter 3

Source: iPRI

A preliminary metrological study (Project Sunchild), conducted in France and Italy during the summer of 2004, compared measurements of UVA and UVB exposure obtained using dosimeters placed near children whilst on holiday with data from the project SoDa which gave information on time spent outdoors, obtained through a questionnaire completed by parents. This comparison showed the possibility of using data provided by SoDa for fine measurement of individual exposure outdoors, in the sun or under cloud cover.

However, the influence of shade from the sun still needed to be determined in order to refine the assessment of individual UV exposure at any given time.

Additional measures were conducted over two days (a sunny day and a day with cloudy periods) to better understand the situations of shade in order to refine the assessment of individual UV exposure at any given time. The measurements obtained were compared with data produced by SoDa, every 20 minutes between 8.00am and 10.00pm. Analysis of the results of this series of measurements showed very high attenuation (80% or more) of ambient UV through the foliage, for both UVA and UVB.

Advantage:

  • Continuous registration of exposure every x minutes for time periods up to several months.

Disadvantages:

  • These two types of devices are costly,
  • They require a calibration step which can be heavy,
  • Constraints imposed by the wearing of the dosimeter,
  • Dosimeters in watch form often only record UVB or erythemal UV,
  • Studies using personal dosimeters suffer from technical and logistical limitations as measurements can be performed only on a limited population size. Furthermore, the measurement angle is limited to 115°.

General note for dosimeters:

A behaviour bias is always suspected, as the knowledge of a dosimeters presence and measure can induce changes in behaviour.